The present invention is a method and compositions containing spin trapping agents for the treatment of dysfunctions and disease conditions arising from oxidative damage.
Oxygenated tissue suffers damage, in many cases permanent damage, if it becomes ischemic and is then reperfused. Brain appears to be highly susceptible to ischemia/reperfusion injury. Certain areas of the brain, for example, the hippocampus and spinal cord, are more susceptible than other regions of the brain. As a result, ischemia/reperfusion injury to brain may have a multiplicative effect simply because of the necessity for complete integrity of all regions in order to have proper functioning.
Free radicals have been postulated to be mediators of reperfusion damage. The most likely sites for production of such radicals as the superoxide (Oxe2x88x922) and hydroxyl (OHxe2x80x94) species, and the precursor oxygen species, H2O2 are the mitochondrial respiratory chain specific enzymes and the sequences catalyzed by cyclooxygenase and lipoxygenase. However, radicals are also formed during autoxidation of many compounds (e.g., catecholamines). Ischemia appears to favor a spurt of free-radical formation, resulting in oxidation of polyenoic free fatty acids, release and reuptake of catecholamines, and oxidation of hypoxanthine by xanthine oxidase. Despite these events occurring during recirculation, when the O2 supply is restored, they represent metabolic cascades triggered by agonist-receptor interactions, energy failure, and/or calcium influx during the insult.
Although free radical formation has been postulated to be a likely cause of ischemic damage, it was difficult to directly demonstrate that such formation occurs and/or that it was sufficiently pronounced to overwhelm the antioxidative defense of the tissue, as reviewed by Curran, et al., Mol. Cell. Biol. 5, 167-172 (1985). Phenyl butyl nitrone (PBN) has been used in a number of these in vitro research studies using spin trapping to look for free radicals, but until demonstrated by the data in U.S. Ser. No. 07/422,651, now U.S. Pat. No. 5,025,032, there has been no data to support the proposition that it could be useful in vivo, particularly with respect to treatment of tissue damage in the central nervous system. In vivo, the drug must be able to both cross the blood brain barrier and act in a manner which reduces tissue damage during or following ischemia.
In U.S. Ser. No. 07/589,177, abandoned on Mar. 5, 1993, the use of PBN and related compounds, as well as 5,5-dimethyl pyrroline N-oxide (DMPO) and xcex1-(4-pyridinyl-1-oxide)-N-tert-butylnitrone (POBN), for treatment of aging was described. Age related changes in central nervous system function have generally been associated with the loss of cells, a widening of lateral ventricles and deficits in short term memory. The precise mechanisms of functional changes as a result of aging, or other diseases associated with aging, have not generally been agreed upon, including several mechanisms for the generation of oxidized material in the brain. A marked reduction in certain neurotransmitter receptor systems has been associated with increased oxidation of proteins. For example, decreases in muscarinic receptors and other cholinergic systems have been characterized as they relate to alterations in functions in Alzheimers disease. It is now known that the processes of aging and Alzheimer""s disease are associated with oxidation of brain proteins. It has also been hypothesized that aging is associated with multiple minor periods of ischemia (multi-infarct conditions or transient ischemia attacks) which, over a period of time, may give rise to the production of oxidized protein.
The demonstration in a variety of systems, both neural and nonneural, that there is an age related enhancement of the level of oxidized protein in tissue gives rise to the possibility that age related dysfunctions in the central nervous system may be associated with the build-up of oxidized proteins and oxidized macromolecules within neurons throughout the central nervous system. The hypothesis is that cells which have a buildup of oxidized protein are less functional and less able to maintain the specified role of those cells in that particular area of the central nervous system. The data presented in U.S. Ser. No. 07/589,177 abandoned on Mar. 5, 1993, was the first report of substantial investigations in which alterations in the oxidized protein burden of the central nervous system was manipulated and correlated with a functional outcome on the part of the animal. There are a number of other disorders and diseases which have now been postulated to be associated with oxidation of proteins, including many central nervous system (CNS) diseases besides stroke and aging, including Parkinsonism, trauma, vascular headaches, cerebral palsy, diabetic neuropathy,and neuroanesthesia adjunct, as well as peripheral nervous system diseases such as diabetic peripheral neuropathy and traumatic nerve damage, as well as peripheral organ diseases. Examples of peripheral organ diseases include atherosclerosis, pulmonary fibrosis, pancreatitis, angioplasty, multiple organ failure, burns, decubitus ulcers, and ischemic bowel disease.
It is therefore an object of the present invention to provide spin-trapping compositions and methods for use thereof which are useful in preventing or reversing ischemic damage in vivo, in the CNS, resulting from diseases such as stroke, aging, Parkinsonism, concussion, Berry aneurysm, ventricular hemorrhage and associated vasospasm, spinal cord trauma, vascular headaches, and neuroanesthesia adjunct.
It is another object of the present invention to provide spin-trapping compositions, and methods for use thereof, which are useful in treating damage in vivo resulting from peripheral nervous system diseases, including diabetic peripheral neuropathy and traumatic nerve damage.
It is still another object of the present invention to provide spin-trapping compositions, and methods for use thereof, which are useful in preventing or reversing free radical damage in vivo resulting from injury, infection and inflammation, especially peripheral organ diseases such as chronic obstructive pulmonary disease (COPD), atherosclerosis (both diabetic and spontaneous), pulmonary fibrosis due to anti-cancer treatment, drug treatment, pancreatitis, angioplasty, multi-organ failure following trauma, burns (chemical, thermal, and radiation), the progressive loss of myocardial cells leading to cardiac failure as a result of age-related oxidation, and ischemic bowel disease.
It is another object of the present invention to provide spin-trapping compositions for use in the process of organ transplantation and preservation.
It is a further object of the present invention to treat disorders not associated with oxidation, such as undesirable HDL/LDL ratios, as well as the treatment of damage arising from exposure to cytotoxic compounds and radiation.
Spin trapping compounds in general have now been discovered to be effective in treating a variety of disorders, including disorders such as those arising from ischemia, infection, inflammation, exposure to radiation or cytotoxic compounds, not just of the central and peripheral nervous systems but of peripheral organ disease having a wide variety of etiologies.
Spin trapping compounds as referred to herein are molecules that (1) have an unpaired electron; (2) form a stable compound or complex with a free radical; and (3) are nontoxic, i.e., have a therapeutic index (margin of safety; EC50/LC50) of 3 or more.
The spin traps provide a unique signal that can be measured by electron spin spectroscopy (ESR) when it binds to a free radical. For example, the oxidation of brain tissue involves a free radical intermediate. Brain tissue that has been treated with PBN has been monitored by ESR. As a free radical on a lipid or protein is generated, PBN traps the radical and forms a covalently bound product with the material, which has a characteristically unique ESR signal. The PBN-(lipid or protein) has then been isolated and identified.
A wide range of spin trapping compounds are disclosed in detail herein. Other spin traps that meet the above three requirements are known to those of skill in the art of organic and medicinal chemistry. An essential criteria for the selection of the spin trap is that it actively trap free radicals without cytotoxicity, and that in the applications where access to the CNS is required for efficacy, that the compounds pass through the blood brain barrier.
Many different disorders can be treated using these compounds, including diseases or disorders of the central and peripheral nervous systems, and disorders arising from ischemia, infection, inflammation, oxidation from exposure to radiation or cytotoxic compounds, as well as due to naturally occurring processes such as aging.